Acting Police Commissioner Viv Rickard says it will take up to a decade to implement changes in the way police deal with sexual assault cases and misconduct by officers.
A third report on police progress since a commission of inquiry five years ago concludes the agency has fully implemented just seven of the 47 recommendations.
Commissioner Viv Rickard told Radio New Zealand's Morning Report programme that progress has been made, but, he said, the commission of inquiry was very clear that this was going to take 10 years.
"This was about the change of actions and behaviours in New Zealand police.
"They've got the monitoring until 2017; they recognised from day one that this wasn't going to be changes that were going to be made overnight."
Mr Rickard says police are working on early intervention strategies to deal with unacceptable behaviour before it escalates into something more serious.
Police Association president Greg O'Connor says the recommendations involve extra layers of bureaucracy at a time when the police budget is being cut by $400 million over four years.
Mr O'Connor says every organisation could always do better, but the police are being pulled in too many directions and, he says, it is not fair to beat them up for a lack of progress.
Resources 'no excuse'
Louise Nicholas, whose allegations against police officers led to the inquiry, says lack of resources is no excuse for not doing a decent job.
Ms Nicholas says police bosses need to treat sex assault investigations as a priority.
She says every single officer needs specialist training, and it is most needed in rural and smaller communities.
In 2007, the commission of inquiry recommended wide changes to the police's handling of sexual assault complaints and organisational culture of the police, following Louise Nicholas's accusations against police and the jailing of officers for raping a woman in Bay of Plenty in 1989.
The Government asked the Auditor-General to monitor the police's progress for a decade, and on Thursday the Deputy Auditor-General, Phillippa Smith, presented her third report.
It described progress as mixed, saying leadership problems remain and most of the commission's 47 recommendations are yet to be finished.
Ms Smith said progress on adult sexual assault investigations is relatively poor and that risks eroding the public's trust in police.
Labour blames budget cuts
Labour Party leader David Shearer says the lack of progress is due to budget constraints preventing the police from taking action.
He says recruiting more women, and giving them more seniority, will go a long way to improving the situation.
Police Minister Anne Tolley says police funding levels were maintained in the budget and Labour is simply scare-mongering and making up figures.